This invention relates generally to vehicle air bag modules and, more particularly, to a passenger-side air bag module of simplified construction that can be used with all currently-available pyrotechnic inflators.
It is becoming more common for vehicle manufacturers to supply passenger vehicles with both driver-side and passenger-side air bag modules. The passenger-side installation is conventionally mounted within the vehicle instrument panel, with air bag deployment through a deployment door located in either the top surface or the front surface of the instrument panel. A front-mounted installation frequently requires a dislocation of the usual glove box. Currently, many air bag module installations are a so-called mid mount, located above the glove box.
In its simplest form, an air bag module consists of an inflator, a container for housing the inflator, an air bag, and an air bag retainer for mounting the air bag to the container, some means for housing or restraining the folded air bag. Conventionally, an air bag module is designed for a specific vehicle, and different vehicles will have different modules.
In addition, the module is usually designed for a specific inflator. Several manufacturers supply passenger-side inflators. Two types of inflator are supplied: directional and thrust-neutral. Both are generally cylindrical, with a nominal diameter of 60 mm, although one available inflator includes a slight outward flare, or taper, at the cap end. In both types, a plurality of discharge holes are provided to provide discharge gas to the air bag for inflation and deployment. These holes are initially covered by foil of different thicknesses which bursts at different pressures to sequentially discharge gas as gas pressure rises.
Directional inflators have a plurality of discharge holes along one side of the inflator casing and produce a net thrust force on the module. They usually include a stud, mounting bolt or other orientation device to assure mounting in a module with the discharge holes oriented to assure gas discharge upwardly out of the container into the air bag.
Directional inflators are frequently mounted with the non-ported sides of the inflator exposed. Because inflator ignition to produce inflation gas results in the inflator casing becoming very hot, a heat shield is sometimes provided to protect the instrument panel innards from excessive heat.
Thrust neutral inflators have discharge holes on opposite sides of the casing, thereby creating no net thrust force on the module. Since inflation gas exhausts from both sides of the inflator, the inflator must be mounted in an enclosed container which will direct inflation gas upwardly out of the container into the air bag.
Conventional air bag modules comprise a plurality of metal stampings which are assembled into a completed module through the use of welds and threaded fasteners in the form of threaded studs, bolts and nuts. These fasteners interconnect various stampings to form the container, mount the air bag retainer to the container, secure the air bag restraint/housing to the container, mount the inflator in the container, mount the heat shield to the module (or to the instrument panel structure, and frequently secure an air bag deployment chute to the assembly. The container usually is secured to a mounting bracket for attachment to the instrument panel supports structure. Also, separate fasteners are used to secure a discharge door to the assembly or to the module mounting bracket.
Thus, distinct air bag modules are required for each specific installation, and for each specific type and shape of inflator. These air bag modules require lengthy assembly time to unite all of the component bits and pieces with a variety of fasteners. Care must be taken to prevent inadvertent mis-assembly of the component parts. As a result, air bag modules are relatively expensive.
It would be desirable to reduce air bag module assembly time and cost. It would also be desirable to provide a passenger-side air bag module which can accommodate all available makes and types of inflators. It also would be desirable to provide an air bag module of reduced complexity and having fewer parts which are simple to assemble. It also would be desirable to provide an air bag module which cannot be mis-assembled.